If you change the X axis Scale DRO from +1.0000 to -1.0000 that will do it (if you have chosen bottom left for the origin X zero, Y zero that will change to bottom right but if you have chosen the centre of the work as the origin then there is no problem).

Hope this helps.

Tweakie.

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thank you for your replyI had also contacted Brett at customer support but had trouble understanding his initial reply.He then sent me some screen shots I now understand.Make Gcode in Mill wizard then open in Mach3.then change the DRO on X axis scale to neg - .Will engrave Mirror.